1. Field of the Invention
The present invention generally relates anti-fuses for use in semiconductor devices. In particular, the invention relates to non-intrinsic anti-fuse structures and methods of making the same.
2. Description of Related Art
Anti-fuses are structures that are electrically open or of very high resistance in their normal state. After programming the structure, the anti-fuse structure becomes electrically conductive. Thus, prior to programming, the anti-fuse is in an “off” state and after programming it is in an “on” state.
Referring to FIG. 1A, a typical vertical anti-fuse structure 100 used in the semiconductor industry has two electrodes 110, 120 embedded in two dielectric layers 111, 121. The electrodes 110, 120 are separated by an anti-fuse layer 130 comprising a dielectric material. Typically, programming the anti-fuse involves applying a voltage across the metal electrodes wherein the applied voltage is in excess of the breakdown voltage of the dielectric material between the metal electrodes. As a result, an electrically conductive filament or “link” 119 forms in the anti-fuse layer and connects the two metal electrodes (See FIG. 1B for a programmed anti-fuse structure 101).
FIGS. 1A and 1B illustrate an intrinsic anti-fuse structure, meaning that in order to program the anti-fuse to create a connection between the metal electrodes, the bulk thickness of the dielectric material 130 between the metal electrodes must be blown (see arrow in FIG. 1A going from electrode 120 across the bulk thickness of anti-fuse layer 130 to electrode 110). The amount of programming voltage required depends upon the breakdown voltage of the anti-fuse layer. And, among anti-fuses within the same chip, the programming voltage will vary from anti-fuse to anti-fuse depending upon the uniformity of the thickness of the anti-fuse layer 130. It is desirable to have anti-fuses with minimum programming voltage which consistently blow at substantially the same voltage throughout the chip.
In addition to high programming voltages, known anti-fuse structures require an extra mask and fabrication steps for integrating the intrinsic anti-fuse structure in the semiconductor device. It is desirable to have an anti-fuse structure which can be made without additional mask and/or processing steps.